The present invention relates to a method of testing a magnetic head for eliminating defective magnetic heads.
In a magnetic media apparatus e.g., magnetic disk drive unit, data are written in and read from a magnetic medium. To maintain reliability of the magnetic head, the magnetic head is tested before handling.
A conventional magnetic head tester is disclosed in Japanese Patent Gazette No. 2004-127511. In the patent gazette, test data are written in a recording medium by a magnetic head, the written date are reproduced by said magnetic head, and the magnetic head is evaluated on the basis of reproduced signals of the reproduced data.
In the conventional method, the test data are written in and read from the magnetic medium, and the good or bad of the magnetic head is evaluated on the basis of the reproduced signals. However, the reproduced signals are influenced by not only characteristics of the magnetic head but also characteristics of the magnetic medium and correlation between the magnetic medium and the magnetic head, e.g., a floating level of the magnetic head from a surface of a magnetic disk.
Therefore, it is difficult to purely evaluate the characteristics of the magnetic head only.
Especially, in a reading element of the magnetic head, a trouble of intermittently increasing and reducing amount of noises in the output signals, which is not caused by external factors, rarely occurs. To eliminate the defected magnetic head by the test, it is desirable to evaluate the magnetic head as a defected head if the amount of noises included in the output signals is increased and reduced from a threshold value at least once. However, the conventional method cannot judge if the amount of noises is varied by influence of the magnetic medium or by the trouble of the magnetic head.